In a shopping center or the like, configured as a set of a plurality of stores, each store usually performs independent business store by store, without sales cooperation among these stores. In general, for example, a store clerk introduces only commodities for sale in the store concerned to customers coming to the store. The store clerk does not introduce to the customers any commodity for sale in the store concerned in combination with commodities in other stores. Also, because the clerk explains and introduces commodities, showing actual commodities, to the customers, it is not possible for the clerk to bring to his store such a commodity for sale in another store, and to introduce this commodity to the customer. Further, even if the clerk introduces the commodity in the other store and the customer purchases this commodity, the sales amount in the original store does not increase. Therefore, the clerk does not conduct such an action of introducing commodities for sale in the other stores.
As such, conventionally, the plurality of stores constituting the shopping center have not conducted sales cooperation although the stores are located in the same shopping center.